sometimes the myth lobby stops updating. so for example the game information or the players in lobby don't show correctly. also player stats etc don't load. the only way to fix it is to leave and re-join the room. This has happened to me about 4-5 times since 1.8.0 beta 1. I often leave myth open in the background for several hours so it is very difficult to say when the updating stops, making re-producing also quite difficult.

another thing: when watching recordigs, units sunk in deep water do not show on overview map.

Yeah definitely graphics driver crashes. I talked to him on Mnet and he has updated his drivers so at this point the only options may be to try D3D, or perhaps OpenGL with UseShaders=false (as Melekor described above) to see if they tend to be less crashy. Otherwise there is always software...

another thing: when watching recordigs, units sunk in deep water do not show on overview map.

Unfortunately we didn't get around to fixing either of these in time for the final version, but we'll keep them in mind for 1.8.1.

For the lobby thing, we don't know why it happens but the pattern seems to be that it is more likely when the 'use multicore' preference is selected. You could try unchecking that and see if it stops happening.

You are logged in when this happens right? Not as a guest? I know guest accounts on Mnet have this issue and I think that is a metaserver side problem. If this happens while logged in, then that sounds like a possible Myth issue. Did you go to preferences and disable "Use Multiple Processors/Cores" to see if it helps?